Question

after 24hrs, only 0.125 GM out of the initial quantity of 1 gm of radioactive isotope remain behind what is its half life period?

Answer 1

half life means time at which concentration becomes half
now,
1g------>0.5g---------->0.25g--------->0.125g
you see concentration continued half
if i let half life is t then 4t time take to cocentration become 0.125
hence , 4t=24 hr
t=6 hr
hence ,
half life =6 hr

Answer 2

Hey !!

Here,

        We are given,    

                                 a = 1 g

                                a - x = 0.125 g

                                t = 24 hours

k = 2.303/t log a/a-x

     = 2.303/24 hr log 1/0.125

         = 0.866 hr⁻¹

t₁/₂  = 0.693/k

      = 0.693/0.866 hr⁻¹

FINAL RESULT = 8.0 hours

GOOD LUCK !!